This invention relates to protein selection methods.
Methods currently exist for the isolation of RNA and DNA molecules based on their functions. For example, experiments of Ellington and Szostak (Nature 346:818 (1990); and Nature 355:850 (1992)) and Tuerk and Gold (Science 249:505 (1990); and J. Mol. Biol 222:739 (1991)) have demonstrated that very rare (i.e., less than 1 in 10.sup.13) nucleic acid molecules with desired properties may be isolated out of complex pools of molecules by repeated rounds of selection and amplification. These methods offer advantages over traditional genetic selections in that (i) very large candidate pools may be screened (&gt;10.sup.15), (ii) host viability and in vivo conditions are not concerns, and (iii) selections may be carried out even if an in vivo genetic screen does not exist. The power of in vitro selection has been demonstrated in defining novel RNA and DNA sequences with very specific protein binding functions (see, for example, Tuerk and Gold, Science 249:505 (1990); Irvine et al., J. Mol. Biol 222:739 (1991); Oliphant et al., Mol. Cell Biol. 9:2944 (1989); Blackwell et al., Science 250:1104 (1990); Pollock and Treisman, Nuc. Acids Res. 18:6197 (1990); Thiesen and Bach, Nuc. Acids Res. 18:3203 (1990); Bartel et al., Cell 57:529 (1991); Stormo and Yoshioka, Proc. Natl. Acad. Sci. USA 88:5699 (1991); and Bock et al., Nature 355:564 (1992)), small molecule binding functions (Ellington and Szostak, Nature 346:818 (1990); Ellington and Szostak, Nature 355:850 (1992)), and catalytic functions (Green et al., Nature 347:406 (1990); Robertson and Joyce, Nature 344:467 (1990); Beaudry and Joyce, Science 257:635 (1992); Bartel and Szostak, Science 261:1411 (1993); Lorsch and Szostak, Nature 371:31-36 (1994); Cuenoud and Szostak, Nature 375:611-614 (1995); Chapman and Szostak, Chemistry and Biology 2:325-333 (1995); and Lohse and Szostak, Nature 381:442-444 (1996)). A similar scheme for the selection and amplification of proteins has not been demonstrated.